I spent a day tripping on shrooms in a sunny London garden in an attempt to solve my deep-seated psychological problems.

Disclaimer: Neither the author nor Tom Fortes Mayer were involved in the supply of illegal drugs. Tom Fortes Mayer agreed to take part to ensure the safety of all participants. VICE does not encourage or condone the use of illegal drugs, obviously.

Now is not the right time for me to meet my inner child. My (largely absent) father has just died, and I'm up – way, way up – on magic mushrooms. Half a dozen other participants are lying on the grass around me, their eyes closed, in a deep hypnotic state. "Think of a time when you felt abandoned or let down by one of your parents," the hypnotherapist guiding the experimental psychedelic therapy session instructs, "and take that scared, angry child by the hand."

I bolt for the "quiet room" – this is too much, much too soon.

Psychedelic hypnotherapy is a new frontier. It's not legal – not in the UK, anyway – but it probably should be. Psychedelics can work miracles. Science says so. Recent studies have shown that, when used correctly, they can rid addicts of their cravings, relieve depression, anxiety and PTSD, induce long-lasting positive behavioural changes, help the terminally ill overcome their terror of death – and even put mere mortals in touch with the divine.

The people attending today have less lofty ambitions. Two want to give up smoking, one wants to overcome her alcohol problem, another to process the death of her mother, and another to overcome deep trauma. But outside lab conditions, will any of it work?

WATCH: How to Use Psychedelics as Safely as Possible

The psychedelics being used by the participants, psilocybin-containing truffles, are Class A drugs, mere possession of which can carry up to seven years in prison, so names and identities have – unless consent was given – been protected.

Organised by myself – with the professional psychiatric oversight of Tom Fortes Mayer, a top hypnotherapist – at a secret location in London, I have high hopes for this enterprise. I've experienced the incredible power of psychedelic hypnosis before. Two years ago, after reading about a study carried out by Johns Hopkins University, which showed that psilocybin had an 80 percent success rate in smoking cessation, I decided to try it out for myself. With Tom's help and a handful of freshly picked magic mushrooms, I achieved in an afternoon what years of painful attempts to go cold turkey and abortive nicotine replacement courses had failed to do. I haven't touched – or even thought about – cigarettes since.

It wasn't hard to find willing participants. Who, after all, wouldn't want to solve their deep-seated psychological problems by getting high in a sunny garden?

The participants were carefully vetted, but allowing half a dozen strangers to dose themselves with powerful drugs in a confined space always has the potential to go wrong. I get to the location early and hide all the knives. There's a massive axe hanging by the backdoor. That certainly has to go.

The attendees are a ragtag bunch. Some have tried psychedelics before; others are virgins. Following the hypnotherapist's instructions, we form a circle of trust and share our intentions for the day.

There's Guy, 55, a musician. "I have a desperate desire to give up smoking," he says. "I've tried pretty much everything. This seems perfect. I know for a fact that psychedelics are a fast-track to the subconscious."

"I experienced a really quite traumatic and painful loss this year, with my mother dying," says Susan, 58, a therapist who has never tried drugs before. "I'm hoping this will help me."

Michelle, 27, a shop manager, has an alcohol problem. "Four years ago, I was sober for six months," she says. "It was the best I've ever felt. I would love for this to take me back there. There's so much more I want to be achieving right now."

Bryan, 22, has come to get over a deeply traumatic event. The last time he took psychedelics was two years ago, with a friend who ended up having a violent psychotic episode. "He was screaming that I was a demon and that he had to kill me, eating sand, punching me hard in the face. It went on for hours. And I was the one who got arrested! I haven't been able to take drugs since. I want to be able to experience them again without fear."

I decide to join in, too. Partly as a canary down the mine, but also because, like Susan, I've recently lost a parent, and haven't even begun to start processing it. Psychedelics, used therapeutically, can help.

It starts off like a cult meeting. Sat in our circle, we take our magic truffles in our hands and hold them up to the blue sky, heads bowed. "We give thanks for this holy sacrament," says the hypnotherapist, "and give our minds and our bodies permission to consume it."

Magic truffles, for all their wonderful qualities, do not taste very holy. They're muddy and bitter and dry. It's like chewing up a mouldy old piece of cork. We pull faces, eat sweet fruit and then lie down to wait. The hypnotherapist guides us gently into the trip.

"I use breathing techniques to bring people into a meditative state which is fearless, present and open, to help them welcome the experience," he explains afterwards. "Then I lay down some programming around the spiritual perspective, so all the psychedelic experiences are unfolding within a spiritual paradigm."

The next few hours are a blur. I lie with my head in a flowerbed. Tears stream freely and silently from the corners of my eyes: my first real weep since the death of my father. I spot Susan in another corner doing exactly the same thing. She looks beatific. At various moments the hypnotherapist takes people away and works with them individually. Those who are capable of speech give long discourses on the beauty of flowers; others just admire them.

At the end of it all I feel clean, energised and imbued with a renewed lust for life. The others seem to feel the same. But did any of it work?

"It was everything it needed to be," says Bryan when I follow up a few days later. "I feel much better, much safer about psychedelics now."

"The drug opened the floodgates," says Susan. "I must have spent a good three quarters of an hour just weeping, free flow, tears pouring. Then I had an intense regression, a return to the womb. Having just experienced the end of my mother's life, I was now returning to the beginning of my life with her. It was really amazing."

For Guy, one of the smokers, and Michelle, with the alcohol problem, success was more limited.

"I felt no cravings afterwards," Guy says. "I felt very clear. When I got home I went straight to bed and slept for 12 hours. But when I woke up I felt a bit of a niggle. I haven't gone back to smoking – but it hasn't gone away entirely. I need another session."

"I drank that night," says Michelle. "But it was because I took acid, coke, ketamine and the rest of the mushrooms at this party afterwards. I was so fucked that the only thing I could think of to help me climb down was to drink. But I didn't drink as much as I usually do, and I haven't drunk since then. I haven't felt any cravings either, so that's pretty good!"

As for me? It will take more than a few magic mushrooms to deal with something as complicated as the death of a father. But it certainly jump-started the process.

Psychedelic therapy isn't a silver bullet. But – considering the research – we should think seriously about making it one of the weapons in the modern therapeutic arsenal. In the USA, things are slowly moving in that direction. For now, under prohibition, it's a risk, but it's not out of reach. All you need is a willing shrink, a sunny garden and a parcel from Amsterdam.